Chapter XXXVIII: Part I: ; Prime’s “Life of Morse,” pp. 168, 265, 266; Gmelin’s

“Chemistry,” Vol. I. p. 317; _Comptes Rendus_ for 1836, Vol. II.
p. 212; Dredge, “Electr. Illum.,” Vol. II. p. 122; Sturgeon,
“Scient. Res.,” Bury, 1850, pp. 13, 37, 216, etc.; Appleton,
“New Am. Cycl.,” Vol. XI. p. 71; _Sci. Am. Suppl._, No. 204, p.
3254; _La Lumière Electrique_ for Oct. 31, p. 202; “Reports of
the Smithsonian Institution” for 1857, pp. 102, 107; for 1862,
pp. 132–143, and p. 127 of last named for Malus’ discovery.
Houzeau et Lancaster, “Bibl. Générale,” Vol. I. part. i. pp.
676–677 detailing the contents of Arago’s “Œuvres Complètes,”
published in thirteen volumes under the direction of J. A.
Barral, also Vol. II. p. 76; _Cornhill Magazine_, Vol. XVII. p.
727; Pierre Prévost, “Tentative,” Genève, 1822 (Poggendorff,
Vol. II. p. 525); _Phil. Mag._, Vol. LVIII. p. 50; Vol. LXI. p.
134; “Abstracts of Papers ... Roy. Soc.,” Vol. II. p. 249.

=A.D. 1821.=--Ridolfi (Marquis Cosimo di), an Italian agriculturist, is the author of several treatises on _fenomeni elettro-magnetici_, published in Florence, wherein he expresses the belief that “because electricity produces both magnetic and calorific phenomena, the elements giving these separately may possibly be so compounded together as to produce electricity; which infers that electricity is a compound of magnetism and caloric.”

REFERENCES.--“Antologia di Firenze,” 1824, p. 159, and “Biblio.
Ital.,” Vol. LXIII. p. 268 for Ridolfi’s description of the
electric plate machine of Novellucci; also “Annales de Chimie et
de Physique,” Vol. X. p. 287; Sturgeon, “Scientific Researches,”
1850, Sec. I. p. 29; “Bibliothèque Universelle” for Feb. 1821.

=A.D. 1821.=--Scoresby (Dr. William) (1789–1857), English master-mariner, and author of numerous scientific and other treatises, first publishes, in the “Trans. of the Edinburgh Society,” accounts of his magnetometer--magnetimeter--and of his electro-magnetic experiments. These were duly followed up by full reports of his many interesting investigations relative, more particularly, to the development of magnetic properties of metals by percussion, as well as to magnetic induction, and regarding the uniform permeability of all known substances to the magnet’s influence.

REFERENCES.--“Abstracts of Papers ... Roy. Soc.,” London
1832–1833, Vol. II. pp. 108, 168, 210; “Dict. of Nat. Biog.,”
London, 1897, Vol. LI. p. 6; _Phil. Trans._ for 1822–1824;
“Trans. Edin. Soc.,” Vol. IX. pp. 243–258, 353, 465; Vol. XI
for 1824; Vol. XII for 1831; Vol. XIII for 1832, and Vol.
XIV for 1833; “Brewster’s Jour. of Sc.,” Vol. VIII for 1828;
“Bibliothèque Britannique,” Genève, 1796, N.S., Vol. XXIX for
1825, p. 185; “Edin. Phil. Jour.” for 1823, Vol. IX. p. 45.

=A.D. 1821.=--Babinet (Jacques) (1794–1872), French scientist, is the author of a very valuable treatise, published in Paris, upon the magnetical discoveries of Oersted, Ampère, Arago, Davy and others. This was followed by his “Résumé complet de la physique,” etc., and by a companion work treating of the relations of ponderable and imponderable bodies to the phenomena of magnetism and electricity, also, during the year 1829, by his Memoir upon the determination of terrestrial magnetism.

He succeeded Savary as Professor at the Collège de France in 1838, and, two years later, took the place of Dulong in the section of General Physics at the Académie des Sciences, becoming not long after the Assistant Astronomer at the Paris Observatory for Meteorology.

His numerous scientific treatises are to be found throughout the “Mémoires de la Société Philomathique,” the “Annales de Physique,” the “Comptes Rendus,” the “Revue des Deux-Mondes” and other prominent publications of the day.

REFERENCES.--Larousse, “Dict. Univ.,” Vol. II. p. 10; “Eng.
Cycl.,” London, 1872, Supplement, p. 143; “Biog. Gén.,” Vol.
IV. p. 21; Mme. Blavatsky, “Isis Unveiled,” Vol. I. p. 202; and
Ronalds’ “Catalogue,” pp. 10–11, for the joint works of Ampère
and Babinet.

=A.D. 1821.=--Pfaff (Christian Heinrich) (1773–1852), who became Professor of Medicine, Physics, etc., at the Kiel University, and was one of the most energetic followers of Volta, sends an unusually interesting communication to Gilbert’s “Annalen der Physik” and to Schweigger’s “Journal für Chemie und Physik,” wherein he very ably supports the views of the Pavia physicist.

Pfaff had, long before that, become favourably known through numerous scientific papers, which were translated into the leading foreign journals, the ones entitled “Dissertatio inauguralis ...” published at Stuttgart, and “Über thierische Elektricität,” published at Leipzig, having brought him special distinction. He had also written, more particularly, upon the experiments made by Alex. von Humboldt as well as relative to Pacchiani’s “Formation of Muriatic Acid by Galvanism,” alluded to at the A.D. 1805 entry, and it was by reason of the investigations made by Pfaff and Van Marum that the use of the voltaic column was generally abandoned. These scientists had constructed very strong piles consisting, in some instances, of as many as seventy large separate discs, when they found that the lower layers of wet cloth or of pasteboard were so seriously compressed by the discs above them as to neutralize their effect.

REFERENCES.--Johann Samuel T. Gehler’s “Phys. Wörterbuch,” Vol.
VI. pp. 507, 517–518; “Roy. Soc. Cat. Sc. Papers,” Vol. IV. pp.
866–871; “Ann. der Chemie,” Vol. XXXIV. p. 307; Vol. LX. p.
314; “Annales de Chimie et de Physique,” Vol. XLI. pp. 236–247;
Sturgeon, “Annals,” Vol. VIII. pp. 80, 146; Noad, “Manual,” p.
558; Wilkinson, “Elements,” Vol. I. pp. 1–8, 18, 22, 196, 326,
407; Vol. II. p. 106; “Encycl. Brit.” ninth ed., Vol. XVIII. p.
725; “Soc. Philom.,” Vol. II. p. 181; _Phil. Mag._, Vol. XXVII.
p. 338.

=A.D. 1821.=--Faraday (Michael), a very distinguished English chemist and natural philosopher (1791–1867), who probably did more for the development of the study of electrical science than any other investigator, publishes his “History of the Progress of Electro-Magnetism” and succeeds, on the morning of Christmas (December 25), 1821, both in causing a magnetic needle to rotate round a wire carrying an electric current and in making the wire rotate around the needle, thus rendering possible the production of continuous mechanical motion by electricity.

The apparatus with which he produced this result is described in nearly all works treating of natural philosophy. Premising his reference to this discovery of Mr. Faraday, whose original papers thereon appear in the _Quarterly Journal of Sciences and the Arts_, Vol. XII. pp. 75, 186, 283 and 416 (the first bearing date September 11, 1821), Dr. Whewell says that on attempting to analyze the electro-magnetic phenomena observed by Oersted and others into their simplest forms, they appeared, at least at first sight, to be different from any mechanical actions which had yet been observed. It seemed as if the conducting wire exerted on the pole of the magnet a force which was not attractive or repulsive, but _transverse_; not tending to draw the point acted on nearer, or to push it further off, in the line which reached from the acting point, but urging it to move at right angles to this line. The forces appeared to be such as Kepler had dreamt of in the infancy of mechanical conceptions, rather than such as those of which Newton had established the presence in the solar system, and such as he, and all his successors, had supposed to be the only kinds of force which exist in nature. The north pole of the needle moved as if it were impelled by a vortex revolving round the wire in one direction, while the south pole seemed to be driven by an opposite vortex (called by Wollaston _vertiginous magnetism_ and considered by Mr. Barlow as the result of _tangential action_). The case seemed novel, and almost paradoxical. It was soon established by experiments, made in a great variety of forms, that the mechanical action was really of this transverse kind. And a curious result was obtained, which a little while before would have been considered as altogether incredible: that this force would cause a constant and rapid revolution of either of the bodies about the other--of the conducting wire about the magnet, or of the magnet about the conducting wire (Vol. XII of the “Journal of the Royal Institution”; Watkins, “Popular Sketch of Electro-Magnetism; or Electro-Dynamics,” London, 1828; Mrs. Somerville, “Connection of Phys. Sciences,” 1846, p. 315).

Passing over many of Faraday’s important scientific investigations in other lines, we come to his second great discovery, that of _magneto-electric induction_, which is the converse of Oersted’s (developed by Ampère and Arago), the production of electricity by magnetism. This is recorded in the first series of “Experimental Researches in Electricity,” read November 24, 1831 before the Royal Society, of which body Faraday had become a Fellow during 1824, and it is published at p. 125 of the _Phil. Trans._ for 1832.

It appears that upon observing certain phenomena, which he described as _Volta-electric_, he concluded before long that magnetism in motion ought to produce an electric current just as electricity was made to imitate all the effects of magnetism. He carried on many experiments, and after the announcements made by Arago to the French Academy, November 22, 1824, he endeavoured to make the conducting wire of the voltaic circuit excite electricity in a neighbouring wire by induction, just as the conductor charged with common electricity would have done, but he obtained no satisfactory results until August 29, 1831 (_Annales de Chimie_, Vol. XLVIII. p. 402). He remarks: “Certain effects of the induction of electrical currents have already been recognized and described; as those of magnetism; Ampère’s experiments of bringing a copper disc near to a flat spiral; his repetition, with electro-magnets, of Arago’s extraordinary experiments, and perhaps a few others. Still it appeared unlikely that these could be all the effects which induction by currents could produce.... These considerations, with their consequence, the hope of obtaining electricity from ordinary magnetism, have stimulated me at various times to investigate experimentally the inductive effects of electric currents. I lately arrived at positive results, and not only had my hopes fulfilled, but obtained a theory which appeared to me to open out a full explanation of Arago’s magnetic phenomena, and also to discover a new state which may probably have great influence in some of the most important effects of electric currents.” His very important conclusion was finally verified, October 1–17, in the following manner. He had taken a helix, or spool of copper wire, which latter, Prof. Brande tells us, was covered with silk as in his former experiments and which was connected by its extremities with a galvanometer, the deflection of which would of course announce a current of electricity in the spiral and wires connected with it, and he found that while in the act of introducing the pole of a powerful bar-magnet within the coils of the spiral, a deflection of the galvanometer took place in one direction, and that when in the act of withdrawing, it took place in the opposite direction; so that each time the conducting wire cut the magnetic curves, a current of electricity was, for the moment, produced in it. Dr. Whewell’s account of the discovery is so well interspersed with references that it deserves repetition here:

“In 1831, Faraday again sought for electro-dynamical induction, and, after some futile trials, at last found it in a form different from that in which he had looked for it. It was then seen, that at the precise time of making or breaking the contact which closed the galvanic circuit, a momentary effect was induced in a neighbouring wire, but disappeared instantly (_Phil Trans._, 1832, p. 127, 1st ser., Art. 10). Once in possession of this fact, Mr. Faraday ran rapidly up the ladder of discovery, to the general point of view. Instead of suddenly making or breaking the contact of the inducing circuit, a similar effect was produced by removing the inducible wire nearer to or further from the circuit (Art. 18)--the effects were increased by the proximity of soft iron (Art. 28)--when the soft iron was affected by an ordinary magnet, instead of the voltaic wire, the same effect still recurred (Art. 37)--and thus it appeared, that by making and breaking magnetic contact, a momentary electric current was produced. It was produced also by moving the magnet (Art. 39)--or by moving the wire with reference to the magnet (Art. 53). Finally, it was found that the earth might supply the place of a magnet in this as in other experiments (2nd ser., _Phil. Trans._, p. 163) and the mere motion of a wire, under proper circumstances, produced in it, it appeared, a momentary electric current (Art. 141). These facts were curiously confirmed by the results in special cases. They explained Arago’s experiments: for the momentary effect became permanent by the revolution of the plate. And without using the magnet, a revolving plate became an electrical machine (Art. 150), a revolving globe exhibited electro-magnetic action (Art. 164), the circuit being complete in the globe itself without the addition of any wire; and a mere motion of the wire of a galvanometer produced an electro-dynamic effect upon its needle (Art. 171).... And thus he was enabled, at the end of his second series of ‘Researches’ (December 1831), to give, in general terms, the law of nature to which may be referred the extraordinary number of new and curious experiments which he has stated (Arts. 256–264), namely, that if a wire move so as to cut a magnetic curve, a power is called into action which tends to urge a magnetic current through the wire; and that if a mass move so that its parts do not move in the same direction across the magnetic curves, and with the same angular velocity, electrical currents are called into play in the mass. And here might properly be added the experimental distinction between a helix and a magnet, which Faraday subsequently pointed out (‘Exper. Res.,’ Art. 3273): ‘Whereas an unchangeable magnet can never raise up a piece of soft iron to a state more than equal to its own, as measured by the moving wire, a helix carrying a current can develop in an iron core magnetic lines of force of a hundred or more times as much power as that possessed by itself when measured by the same means.’”

An article on the reduction of Mr. Faraday’s discoveries in magneto-electric induction to a general law appeared in the “Philosophical Transactions of the Royal Society” Vol. III. p. 37, and at Vol. IV. p. 11, new series, of the _Philosophical Magazine_ (see Faraday’s first two Memoirs in the _Phil. Trans._, Book XIII. chaps. v and viii; letter to Gay-Lussac in _Annales de Chimie_, Vol. LI. 1832, pp. 404–434; _Phil. Mag._, Vol. XVII. pp. 281, 356); while, in the _Phil. Trans._ for 1832, p. 132, is the Report of his production of the electric spark through a modified arrangement in which the electric current was induced by an electro-magnet, as shown in his subsequent work published in London during 1834. This is alluded to in Vol. V. pp. 349–354 of the _Phil. Mag._ for latter year, and in Poggendorff’s _Annalen_, Vol. XXXIV. pp. 292–301 for 1835. (See also Bakewell, “Elect. Science,” pp. 39, 140, 144.)

“Around the magnet, Faraday
Is sure that Volta’s lightnings play;
But how to draw them from the wire?
He took a lesson from the heart
’Tis when we meet--’tis when we part,
Breaks forth the electric fire.”

HERBERT MAYO, in _Blackwood_.

In Prof. Alfred M. Mayer’s address, delivered before the American Association at Boston, August 26, 1880, we read: “It is not generally known or appreciated that Henry and Faraday independently discovered the means of producing the electric current and the electric spark from a magnet. Tyndall, in speaking of this great discovery of Faraday, says: ‘I cannot help thinking while I dwell upon them, that this discovery of magneto-electricity is the greatest experimental result ever obtained by an investigator. It is the Mont Blanc of Faraday’s own achievements. He always worked at great elevations, but higher than this he never subsequently attained.’ And it is this same physicist who further remarks (‘Johnson’s Cycl.,’ Vol. II. pp. 26–27) that all our induction coils, our medical machines, and the electric light so far as it has been applied to lighthouses, are the direct progeny of Faraday’s discovery. In the paper here referred to (Nov. 24, 1831) he for the first time calls the ‘magnetic curves,’ formed when iron-filings are strewn around a magnet, ‘lines of magnetic force.’ All his subsequent researches upon magnetism were made with reference to those lines. They enabled him to play like a magician with the magnetic force, guiding him securely through mazes of phenomena which would have been perfectly bewildering without their aid. The spark of the _extra current_, which I believe was noticed for the first time by Prof. Joseph Henry, had been noticed independently by Mr. William Jenkin. Faraday at once brought this observation under the yoke of his discovery, proving that the augmented spark was the product of a secondary current evoked by the reaction of the primary upon its own wire.” The phenomenon of the spark from the _extra current_ here alluded to was first announced by Henry in July 1832. He had observed that when the poles of a battery are united by means of a short wire of low resistance, no spark or at least a very faint one is produced, but when the poles of the battery are connected by a long copper wire and mercury cups, a brilliant spark is obtained at the moment the circuit is broken by raising one end of the wire out of its cup of mercury and also that the longer the wire and the greater the number of its helical convolutions, the more powerful would be the effect (Silliman, “Am. Jour. of Sc.,” Vol. XXII). The results of Faraday’s investigation of the _extra current_ first appeared in the _Phil. Mag._ for November 1834.

The references already named give an account of many other important results attained by Faraday during 1831 and up to the date of the publication of the third series of his “Experimental Researches” (p. 76), wherein he recognizes the “Identity of Electricities derived from different sources”[60] (Vol. I. par. 265 and 360), after investigating the electricities of the machine, the pile, and of the electrical fishes, and after employing as conductors the entire plant of the metallic gas pipes and water pipes of the city of London (_Phil. Trans._ for 1833, p. 23; Poggendorff, _Annalen_, Vol. XXIX, 1833, pp. 274, 365).

In the fourth series, relating to “A New law of electric conduction” (Vol. I. par. 380, 381, 394, 410), he demonstrates the influence of what is called “the state of aggregation” upon the transmission of the current. He found that although the latter was conveyed through water it did not pass through ice. This he subsequently explained by saying that the liquid condition enables the molecule of water to turn round so as to place itself in the proper line of polarization, which the rigidity of ice prevents. This polar arrangement must precede decomposition, and decomposition is an accompaniment of conduction (_Phil. Trans._ for 1833, p. 507; Poggendorff, _Annalen_, Vol. XXXI, 1834, p. 225; also _Phil. Mag._, Vol. X. p. 98; “Royal Inst. Proc.,” Vol. II. p. 123; Silliman’s _Journal_, Vol. XXI. p. 368).

Other series (pars. 309, 450, 453–454, 472, 477, 661–662, 669, etc.) treat of “Electro-chemical or electrolytic decomposition.” The experiments of Wollaston in this line have been given under the A.D. 1801 date, where Prof. Faraday’s opinion of them is also expressed. Faraday was successful in the employment of Wollaston’s apparatus for the decomposition of water, and he afterwards devised an arrangement enabling him to effect true electro-chemical decompositions by common electricity as well as by the voltaic pile. For this, it is said, he used an electric battery consisting of fifteen jars and a plate machine having two sets of rubbers and a glass disc fifty inches in diameter, the whole presenting a surface of 1422 inches. One revolution of the plate could be made to give ten or twelve sparks, each one inch long, while the conductors afforded sparks ten to fourteen inches in length. He also devised a _discharging train_, to instantaneously carry off electricity of the feeblest tension by connecting a thick wire as he had previously done with the London gas and water pipes. A good description of the methods by which he succeeded with the latter apparatus in establishing the analogy between ordinary and voltaic electricity is given in the eighth “Britannica,” Vol. VIII. pp. 596–597. He had shown, at paragraph 371 and p. 105 of his “Researches,” that as a measure of quantity, a voltaic group of two small wires of platinum and zinc, placed near each other, and immersed in dilute acid for three seconds, yields as much electricity as the electrical battery, charged by thirty turns of a large machine; a fact that was established both by its momentary electro-magnetic effect, and by the amount of its chemical action, but, in order to enable him to establish a principle of definite measurement, he devised a _voltameter_ or _volta-electrometer_ as mentioned at paragraph No. 739 (Noad, “Manual,” p. 365). By means of this apparatus he calculated that a single grain of water in a voltaic cell will require for its decomposition a quantity of electricity equal to that liberated in 800,000 discharges of the great Leyden battery of the Royal Institution (“Researches,” par. 861). Also, that the decomposition of a single grain of water by four grains of zinc in the active cell of the voltaic circle, produces as great an amount of polarization and decomposition in the cell of decomposition, as 950,000 charges of a large Leyden battery, of several square feet of coated surface; an enormous quantity of power, equal to a most destructive thunderstorm. Tyndall remarks (“Notes on Electricity,” No. 118, also “Faraday as a Discoverer,” 1868, p. 44) that Weber and Kohlrausch ascertained that the quantity of electricity associated with one milligramme of hydrogen in water, if diffused over a cloud 1000 metres above the earth, would exert, upon an equal quantity of the opposite electricity at the earth’s surface, an attractive force of 2,268,000 kilogrammes.[61]

Faraday introduced new terms to express more specifically the circumstances attending electro-chemical decomposition. Objections had long been made to the designation _poles_--one _positive_, the other _negative_--on the ground that such did not convey a correct idea of the effects produced. These designations had been given under erroneous supposition that the poles exerted an attractive and repulsive energy towards the elements of the decomposing liquid, much as the poles of the magnet act towards iron. When connecting the extremities of a battery, the electricity simply makes a circuit; the current passes _through_ the substance to be decomposed and the elements remain in operation until the connection is broken. Since the poles merely act as a path to the current he calls them electrodes (_electron_, electricity, _odos_, a way); that part of the surface of the decomposing matter which the current enters--immediately touching the positive pole--he designates as _anode_ (_ana_, upward) and the part of the matter which the current leaves--next to the negative pole--_cathode_ (_kata_, downward). He names _electrolyte_ (_luo_, to set free) the fluid decomposed directly by electricity passing through it; the term _electrolyzed_ meaning electro-chemically decomposed. The elements of an _electrolyte_ are named _ions_ (_ion_, going), the _anion_ being the body (in sulphate of copper solution, the acid) which _goes up_ to the positive pole, to the _anode_ of the decomposing body, whilst the _cation_ is that (in sulphate of copper solution, the metal) which _goes down_ to the negative pole, to the _cathode_ of the decomposing body.

The many tests which he made with his voltameter led him to the conclusion “that under every variety of circumstance, the decompositions of the voltaic current are as definite in their character as those chemical combinations which gave birth to the atomic theory” (_Phil. Trans._ for 1833, p. 675; for 1834, p. 77; Poggendorff, _Annalen_, Vols. XXXII. p. 401; XXXIII. pp. 301, 433, 481; Bakewell, “Electric Science,” p. 124; “Brit. Assoc. Report” for 1833, p. 393; Henry’s “Memoirs of Dalton,” p. 106).

The eighth series of his “Researches” (Vol. I. pars. 875, etc.) treats of the “electricity of the voltaic pile,” a further investigation of which is shown through the papers constituting his sixteenth and seventeenth series as per Index of Vol. II. p. 302. Faraday establishes by very simple experiments the most powerful known refutation of Volta’s contact theory and shows conclusively that the current in the pile results from the mutual chemical action of its elements, just as Fabbroni and Wollaston had stated before him. An extract from the conclusion of his very elaborate defence of the chemical theory reads as follows: “... the contact theory assumes, that a force which is able to overcome powerful resistance ... can arise out of nothing: that, without any change in the acting matter, or the consumption of any generating force, a current can be produced, which shall go on for ever against a constant resistance, or only be stopped as in the voltaic trough, by the ruins which its exertion has heaped upon its own course.... The chemical theory sets out with a power, the existence of which is pre-proved, and then follows its variations, rarely assuming anything which is not supported by some corresponding simple chemical fact. The contact theory sets out with an assumption to which it adds others, as the cases require, until at last the contact force, instead of being the firm unchangeable thing at first supposed by Volta, is as variable as chemical force itself. Were it otherwise than it is, and were the contact theory true, the equality of cause and effect must be denied. Then would perpetual motion also be true; and it would not be at all difficult, upon the first given case of an electric current by contact alone, to produce an electro-magnetic arrangement, which, as to its principle, would go on producing mechanical effects for ever” (“Exp. Res.,” pars. 2071–2073, Vol. II. pp. 103–104; _Phil. Trans._ for 1834, p. 425; for 1840, pp. 61, 93; Poggendorff, _Annalen_, Vols. XXXV. pp. 1, 222; LII. pp. 149, 547; LIII. pp. 316, 479, 548. Auguste Arthur De la Rive, “Archives de l’Elect.,” Genève, 1841–1845, Vol. I. pp. 93, 342; Graham, “Elem. of Chem.,” London, 1850, Vol. I. pp. 242, etc.; Faraday and Sturgeon, “Ann. of Elec.,” Vol. IV. pp. 229, 231; Daniell, “Intro. to Study of Chem. Phil.”; Liebig, _Annal._, Vol. XXXVI. p. 137; Figuier, “Expos. et Hist.,” 1857, Vol. IV. p. 434. Also De la Rive’s “Treatise,” Vol. I. pp. 393–402; “Exper. Researches,” Vol. I. pp. 322–323--induction of galvanic current upon itself).

Faraday’s theory of induction offers nothing new as to the nature of the electric forces--it simply indicates the manner of their distribution and the laws by which they are affected. His experiments show that electrization by influence is possible only by means of continuous particles of air or other non-conducting medium (dielectric), that no electric action occurs at a distance greater than the interval existing between two adjacent molecules of such medium, in which latter a true polarization of the particles takes place, and that it is by means of this polarization that electric force is transferred to a distance. Induction only takes place through insulators: induction is insulation, it being the action of a charged body upon insulating matter, of which latter the particles communicate to each other in a very minute degree the electric forces whereby they become polarized and are enabled to transmit an equal amount of the opposite force to a distance. The latter property is termed _inductive force_ or _specific inductive capacity_, and Faraday discovered that the intensity of electric induction varies in different insulating media; for instance, the induction through shell-lac (the first substance he experimented with) being twice as great as through a like thickness of air. It was while experimenting with shell-lac that he first observed the singular phenomenon of the _return_ or _residual charge_, i. e. the charge which would of itself gradually reappear in the apparatus after the latter had been suddenly and perfectly discharged. This, he considered due to the penetration, into the substance of the dielectric, of a portion of the charge by conduction. The inductive capacity of all gases he found to be the same as that of air, and this property does not alter with variations in their density.

His discovery of the specific inductive capacity of various substances has been already alluded to (A.D. 1772, Cavendish). Faraday’s biographer in the ninth “Britannica” says: “It appears, from hitherto unpublished papers, that Henry Cavendish had, before 1773, not only discovered that glass, wax, rosin and shell-lac have higher specific inductive capacities than air but had actually determined the numerical ratios of these capacities. This, of course, was not known to Faraday or other electricians of his time.” It was on the 30th of November, 1837, Faraday communicated to the Royal Society the paper on Induction wherein he announces the re-discovery of _specific inductive capacity_. One of its most important results to-day, remarks John Tyndall, “is the establishment of the specific inductive capacity of insulators--a subject of supreme importance in connection with submarine cables. As a striking illustration of Faraday’s insight, it may be mentioned that as early as 1838 he had virtually foreseen and predicted the retardation produced by the inductive action between the wires of submarine cables and the surrounding sea-water” (Tyndall’s “Notes on Electricity,” 1871, pp. 160–161; “Exper. Researches,” Index Vol. I.; “Faraday as a Discoverer,” new edition, p. 89). Consult, also, the references entered at Cavendish, A.D. 1772; J. E. H. Gordon, “Phys. Treatise on Elect. ...” London, 1883, Vol. I. chap. xi. par. 81–83, which alludes to “Exper. Researches,” 1161, Vol. I. p. 360 as well as to the investigations of specific inductive capacities made by Boltzmann, Romich and Fajdiga, Romich and Nomak, Schiller, Silow, Wüllner, Dr. Hopkinson, J. E. H. Gordon, Ayrton and Perry, and gives the “General Table of Specific Inductive Capacities,” detailing the observations of Cavendish, Faraday and all the others named above. See, besides, “Reprint of Papers ...” Sir Wm. Thomson, 1872 to 1884, 2nd ed., paragraphs 36, 46, 50; _Phil. Trans._, 1838, pp. 1, 79, 83, 125; 1842, p. 170; Poggendorff, _Annalen_, Vols. XLVI. pp. 1, 537; XLVII. pp. 33, 271, 529; XLVIII. pp. 269, 424, 513; XCVI. p. 488; XCVII. p. 415; _Phil. Mag._, Vols. IX. p. 61; XI. p. 10; XIII. pp. 281, 355, 412; “Bibl. Univ.,” Vol. XVII. p. 178 and “Archives des Sc. Phys.,” Vol. XXXI. p. 48; “Journal de Pharm.,” Vol. XXVII. p. 60; W. S. Harris, “Specific Inductive Capacities ...” (_Phil. Trans._, 1842).

In the fifteenth series of his “Exper. Researches” (Vol. II. pars. 1749–1795), Faraday gives the results of his experiments proving the identity of the power of the _gymnotus_ or the _torpedo_ with common electricity. He concludes that “a single medium discharge of the fish is at least equal to the electricity of a Leyden battery of fifteen jars, containing 3500 square inches of glass coated on both sides, charged to its highest degree” (p. 8); “all the water and all the conducting matter around the fish, through which a discharge circuit can in any way be completed, is filled at the moment with circulating electric power and this state might be easily represented generally in a diagram by drawing the lines of inductive action upon it. In the case of a _gymnotus_ surrounded equally in all directions by water, these would resemble generally in disposition the magnetic curves of a magnet having the same straight or curved shape as the animal, that is, provided he in such cases employed, as may be expected, his four electric organs at once” (p. 12) (C. Matteucci, “Traité des phénom. ...” Paris, 1844, pp. 188–192).

Then follow in due course, Faraday’s remarkable papers relating to the magnetization of light and the illumination of magnetic lines of force, the polar and other condition of diamagnetic bodies, etc. These communications, which he made to the Royal Society in November and December 1845, contain the particulars of what many consider to be his most brilliant discoveries. He first shows that when a ray of polarized light passes through a piece of silicated borate of lead glass placed between the poles of a natural (or preferably an electro-) magnet, so that the line of magnetic force shall pass through its length, the polarized ray will experience a rotation. The law is thus expressed: “If a magnetic line of force be _going_ from a North pole or coming from a South pole, along the path of a polarized ray, _coming_ to the observer, it will rotate that ray to the right hand, or if such a line of force be coming from a North pole or going from a South pole it will rotate such a ray to the left hand” (_Phil. Trans._ for 1846 and 1856; Poggendorff, _Annalen_, Vol. C. pp. 111, 439; Noad, “Manual,” pp. 804–805; Harris, “Rud. Mag.,” Parts I and II. p. 71; Whewell, “Hist. of the Inductive Sciences,” Vol. II. pp. III, 133; Gmelin’s “Chemistry,” Vol. I. pp. 168–169). At the Faraday Centenary Celebration held in London, June 18, 1891, Lord Rayleigh observed that “the full significance of the last-named discovery was not yet realized. A large step towards realizing it, however, was contained in the observation of Sir William Thomson, that the rotation of the plane of polarization proved that something in the nature of rotation must be going on within the medium when subjected to the magnetizing force, but the precise nature of the rotation was a matter for further speculation, and perhaps might not be known for some time to come.”

Through Faraday’s other communication, is made known the discovery of _diamagnetism_. Therein he shows, as the result of his customary careful experimental explorations that the magnetism of every known substance (even tissues of the human frame) is manifested in one of two ways. Either the body is, like iron, attracted by the magnet, taking a position coincident with the magnetic forces which he calls _paramagnetic_ (_para_ beside or near, _magnetes_, _magnes_, magnet) or bodies--like bismuth, for instance--are repelled by the poles and should therefore be called _diamagnetic_ (_dia_, across) for they set themselves across, equatorially, or at right angles to the magnetic lines. As far back as 1788, the repulsion by bismuth was first observed by Brugmans, while M. Becquerel, during 1827, confirmed the observation, said to have been made by Coulomb, that a needle of wood could be made to point across the magnetic curves, and stated that he had found such a needle place itself parallel to the wires of a galvanometer. Yet, neither M. Becquerel nor M. Lebaillif, who (after Saigy and Seebeck) had called attention to the repulsion of both bismuth and antimony by the magnet, made a distinction of the diamagnetic force from the paramagnetic as Faraday did. Amongst other results, this English scientist found that phosphorus is at the head of all diamagnetic substances, bismuth taking the lead amongst the metals, whilst, of many gases and vapours, oxygen proved to be the least diamagnetic, in fact, the only one which is paramagnetic (“Lond., Edin., and Dub. Phil. Mag.” for December 1850). All the facts set forth in Mr. Faraday’s paper are, according to Brande, resolvable by induction into the general law; that while every particle of a magnetic body is attracted, every particle of a diamagnetic body is repelled by either pole of a magnet: these forces continue as long as the magnetic power is sustained, and cease on the cessation of that power, standing therefore in the same general antithetical relation to each other as the positive and negative conditions of electricity, the northern and southern polarities of ordinary magnetism, or the lines of electric and magnetic force in magneto-electricity. (_Phil. Trans._ for 1846–1851; _Phil. Mag._, Vols. XXVIII. pp. 294, 396, 455; XXIX. pp. 153, 249; XXXVI. p. 88; _Annales de Chimie_, Vol. XVII. p. 359; Poggendorff, _Annalen_, Vols. LXVIII. p. 105; LXX. p. 283; LXXXII. pp. 75, 232; “Bibl. Univ. Archives,” Vols. I. p. 385; III. p. 338; XVI. p. 89; Ludwig F. von Froriep, “Notizen,” Vols. XXXVII. cols. 6–8; XXXIX. col. 257; Erdmann, “Jour. Prak. Chem.,” Vol. XXXVIII. p. 256; Liebig, _Annal._, Vol. LVII. p. 261; Napoli, “Rendiconto,” Vol. VI. p. 227; Silliman’s “Journal,” Vols. II. p. 233; X. p. 188; Walker, “Elect. Mag.,” Vol. II. p. 259; John Tyndall, “Researches on Diamagnetism and Magne-crystallic Action,” London, 1870, pp. 1, 38, 89, 90, 137; Whewell, “Hist. of Ind. Sc.,” 1859, Vol. II. p. 620; “Athenæum” for January 31, 1846; Plücker’s paper “On the relation of Magnetism and Diamagnetism,” dated September 8, 1847, in Poggendorff’s _Annalen_ and in Taylor’s “Scientific Memoirs,” Vol. V. part ix. p. 376; Edmond Becquerel’s “Memoir on Diamagnetism” in _An. de Ch. et de Ph._, Vol. XXXII. p. 112; “Practical Mech. and Engin. Mag.,” 1846, p. 117; for “Coexistence of Paramagnetism and Diamagnetism in same Crystal,” _see_ “Jour. of Chem. Soc.,” London, February 1906, p. 69, taken from _Les Comptes Rendus_).

During the course of Faraday’s experiments to ascertain the effects of magnetism on crystals some very curious results were obtained with bismuth. Having suspended four bars of the metal horizontally between the poles of the electro-magnet, the first pointed _axially_; the second _equatorially_; another _equatorial_ in one position, and _obliquely equatorial_ if turned round on its axis fifty or sixty degrees; the fourth _equatorially and axially_ under the same treatment; whilst all of them were repelled by a single magnetic pole, thus showing their strong and well-marked diamagnetic character. These variations were attributed to the regularly crystalline condition of the bars. He then chose carefully selected crystals and, after describing their peculiar action between the poles, he says that “the results are altogether very different from those produced by diamagnetic action. They are equally distinct from those dependent on ordinary magnetic action. They are also distinct from those discovered and described by Plücker, in his beautiful researches into the relation of the optic axis to magnetic action; for there the force is equatorial, whereas here it is axial. So they appear to present to us a new force, or a new form of force in the molecules of matter, which, for convenience’ sake, I will conventionally designate by a new word, as the _magne-crystallic force_.” Prof. A. M. Mayer justly observes (“Johnson’s Cycl.,” I. 1342) that the above-named facts “received their full explanation at the hands of Tyndall, whose subtile examination or lucid explanation of these phenomena--though not popularly known--we think form his greatest claim to illustrious distinction as a man of science.” For an extract from the last-named work relative to M. Poisson’s remarkable theoretic prediction of magne-crystallic action, see the article concerning that scientist at A.D. 1811. (Consult _Phil. Trans._ for 1849, pp. 4, 22; _Phil. Mag._, Vol. XXIV. p. 77 and s. 4, Vol. II. p. 178; De la Rive, “Treatise,” Vol. I. pp. 482–497; “Athenæum,” No. 1103, p. 1266; Gmelin’s “Chemistry,” Vol. I. pp. 514–519.)

The remarkable discoveries we have named were succeeded by many others of a very high order, the references to which occupy as many as 158 separate entries through pp. 555–560, Vol. II. of the “Catal. of Sci. Papers of the Royal Society.” Among those may be singled out his additional investigations regarding the magnetism of gases and the magnetic relations of flames and gases, the lines of magnetic force, subterraneous electro-telegraphic wires (_Phil. Mag._ s. 4, Vol. VII. 1854), the relation of gravity to electricity, atmospheric magnetism, likewise his recorded observations on hydro-electricity, magneto-electric light for lighthouses, pyro-electricity, the electrophorus, Wheatstone’s telegraph, etc. (“Roy. Inst. Proc.” for 1854–1858, pp. 555–560). It was in 1848 he wrote of the powerful insulating properties of gutta-percha (Gmelin’s “Chemistry,” Vol. I. p. 313; “Lond. and Edin. Phil. Mag.,” Vol. XXXII. p. 165), and he not long after constructed a very singular apparatus to a Leyden jar consisting of a wire 140 miles long, perfectly insulated with gutta-percha, one end of which communicated with an insulated pile of 360 elements of zinc and copper charged with acidulated water, as described in the “Britannica.” The results of his inquiries concerning the Leyden jar charge of buried electric conducting wires were, according to Whitehouse’s pamphlet on the Atl. Tel. (p. 5) communicated to the Roy. Inst. during the year 1854.

The life of Michael Faraday is an admirable example of extraordinary successes achieved through patient endeavour and constancy of purpose over unusual obstacles of birth and education. M. Dumas, in the sixteenth volume of the London “Chemical News,” tells us he was the only man in England who raised himself to the first rank in science, whose every attribute can be fearlessly held up as a model. He had none of the “ambition, eternal pining after rank or hauteur” of Davy, nor “the secretiveness and coldness” of Wollaston. “Faraday’s intellect, while it burnt as brightly as Davy’s, was as deep searching as Wollaston’s, and as reverent as Newton’s, yet it had nothing in it which could repel us, chill us, or forbid our affection.” The son of a blacksmith, he was first placed in a bookseller’s shop, then apprenticed to a bookbinder, but his tastes were averse to the trade and he was led to seek instruction in another line, more particularly after attending the evening lectures of Mr. Tatum, yet, as already stated (see Dr. George Gregory, A.D. 1796), it was while in M. Riebau’s (the bookbinder’s) employ that chance threw in his way the works which led him to enter the channels in which he subsequently became so distinguished. To a friend, he writes:

“Your subject interested me deeply every way; for Mrs. Marcet was a good friend to me, as she must have been to many of the human race. I entered the shop of a bookseller and bookbinder at the age of thirteen, in the year 1804, remaining there eight years, and during the chief part of the time bound books. Now it was in those books, in the hours after work, that I found the beginning of my philosophy. There were two that especially helped me, the ‘Encyclopædia Britannica,’ from which I gained my first notions of electricity, and Mrs. Marcet’s ‘Conversations on Chemistry,’ which gave me my foundation in that science. Do not suppose that I was a very deep thinker, or was marked as a precocious person ... but facts were important to me and saved me. I could trust a fact and always cross-examined an assertion. So when I questioned Mrs. Marcet’s book by such little experiments as I could find means to perform, and found it true to the facts as I could understand them, I felt that I had got hold of an anchor in chemical knowledge, and clung fast to it....” (“Faraday as a Discoverer,” by John Tyndall, 1868, pp. 6–7).

Think of the startling, not to say marvellous, achievements growing out of Faraday’s subsequent first experiments with an electrical machine made out of an old bottle and by the aid of a Leyden jar constructed with a medicine phial!

In 1812, he was taken by Mr. Dance to the lectures of Sir Humphry Davy, whose chemical assistant he became the following year and in whose company, as we have already seen (A.D. 1801), he travelled on the Continent until 1815. Mr. Davies Gilbert, to whom is due Davy’s introduction to the Royal Institution, has said of the last-named illustrious philosopher that the greatest of all his discoveries was the discovery of Faraday. In 1816, Michael Faraday was placed by Mr. Brande in charge of the “Quarterly Journal of Science,” and, during 1823, he was elected corresponding Member of the French Academy, becoming F.R.S. the ensuing year through the influence of his friend Richard Phillips. It was during 1825–1826 he published in the _Phil. Trans._ the chemical papers wherein he announces the discovery of benzole (called by him bicarburet of hydrogen) to which, says Hoffmann, “we virtually owe our supply of aniline, with all its magnificent progeny of colours.” In 1827, Faraday succeeded Davy as lecturer at the Royal Institution, and, from 1829 to 1842, he occupied the post of chemical lecturer at the Royal Military Academy, Woolwich. The “Experimental Researches,” to which we have so often alluded, first appeared in the 1831 _Phil. Trans._, and were afterwards collected in three volumes, which were published respectively during 1839, 1844, 1855. Faraday was made D.C.L. in 1832 by Oxford University, and, one year later, he received the Fullerian professorship of chemistry in the Royal Institution, which he held till his death. A pension was given him by the English Government in 1835, and he also received the Royal Medal, which latter was again conferred upon him, together with the Rumford Medal, during 1846. Ten years before (1836) he had become a member of the Senate of the London University, and during the year 1858 the Queen allotted him the residence in Hampton Court where he died in 1867. “Taking him for all in all,” says Tyndall, “it will, I think, be conceded that Faraday was the greatest experimental philosopher that the world has ever seen; and I would hazard the opinion that the progress of future research will tend not to diminish but to enhance the labours of this mighty explorer.”

REFERENCES.--“Life of Faraday,” by Dr. H. Bence Jones (Sec.
R.I.); “Michael Faraday,” by Dr. J. H. Gladstone, 1872; “Faraday
as a Discoverer,” by John Tyndall; the biographical sketch by
Prof. Joseph Lovering; “Michael Faraday, his Life and Work,”
by Silv. P. Thompson, New York, 1898; “The Chemical News” (Am.
Rep.), Vol. I. pp. 246, 250, 276, and Vol. II. pp. 98, 202;
Report of the Faraday Centenary celebration at the London
Roy. Inst., June 17, 1891; Poggendorff, Vol. I. pp. 719–722;
Larousse, “Dict. Univ.,” 1872, Vol. VIII. p. 99; “Biog. Gén.,”
Vol. XVII. pp. 90–93; “Men of the Time,” London, 1856; Reports
on Faraday’s Lectures delivered before the Roy. Inst. (taken
from the “London Mining Journal,” Nos. 714, 717–722), at pp.
319–324, 387–393; Vol. XVIII for 1849 of “Jour. of Frankl.
Inst.”; Gmelin’s “Chemistry,” Vol. I. pp. 424, etc., 435–436,
514–519; Poggendorff, _Annalen_, Vols. LXXXVIII. p. 557;
Ergänz, Vol. I. pp. 1, 28, 64, 73, 108, 187, 481–545; Gustav
Wiedemann, “Die Lehre von Galv.,” 1863 and “Die Lehre von der
Elektricität,” 1883; W. H. Uhland, “Die Elektrische Licht,”
1884, p. 62; An. Sc. Dis. for 1850, pp. 129, 131, 132; for 1851,
p. 133, and for 1852, p. 110 on “Atmospheric Magnetism,” taken
from “Jameson’s Journal,” July 1851; for 1853, p. 132; for
1856, p. 161; for 1858, p. 177, Faraday, “On the Conservatism
of Force”; for 1860, p. 125, Faraday on “Static Induction”; for
1863, p. 108, “Elec. Lamp in Lighthouses”; for 1868, p. 169;
for 1870, p. 10; for 1874, p. 174, on “Dielectric Absorption”;
Robison, “Mechan. Phil.”; Leslie, “Geomet. Anal.”; “Jour. Roy.
Inst.” for February 1831, Vol. I. p. 311 (Electrif. of ray of
light); eighth “Britannica,” Vols. I, sixth dissertation; VIII.
pp. 532–533, 539, 542, 544, 552, 601, 607, 617; XIV. pp. 68,
663; XXI. pp. 612, 622, 628, 630; ninth “Britannica,” Vol. IX.
pp. 29–31; Brockhaus, “Conversations-Lexikon,” Vol. VI. pp.
565–566; “Lond. and Edin. Ph. Mag.,” Vol. I. p. 161 for letter
of Faraday of July 27, 1832, enclosing one signed P. M., “in
which _chemical decomposition is for the first time obtained by
the induced magnetic current_”; Faraday and Schönbein (“London
and Edin. Mag.,” July-August 1836; “Roy. Instit. Proc.,” III.
70–71); Faraday and Riess, “On the action of non-conducting
bodies in electric induction,” 1856; Sturgeon, “Sc. Res.,” 1850,
pp. 20, 475; “Practical Mechanic,” Vols. II. pp. 318, 408; III.
p. 197; “Libr. of Useful Knowledge” (Elec. Mag.), pp. 18, 99;
Humboldt, “Cosmos,” Vol. I. pp. 182, 188; Harris, “Rud. Magn.,”
1852, I and II, pp. 61–69, etc., 199; III. 122–128 and “Rud.
Elec.,” 1st ed., pp. 33–34; “Edin. Jour. Sc.,” 1826, Vol. III.
p. 373; “Edin. new Ph. Jour.,” Vol. LI. p. 61; Golding Bird’s
“Nat. Phil.,” p. 227; James Johnstone, “The Ether Theory of
1839,” pp. 26, 37; Noad, “Manual,” pp. 59, 236, 692, 805, 866;
“Am. Jour. Sc.” for April 1871, relative to lines of magnetic
force; “Ann. of Phil.” for 1832; “Bibl. Univ. Archives,” Vol.
XVI. p. 129; “Roy. Instit. Proc.,” Vol. I, 1851–1854, pp. 56,
105, 216, 229; _Phil. Trans._, 1832, p. 163; 1851, pp. 29, 85;
1852, pp. 25, 137; _Phil. Mag._, Vol. III, 1852, p. 401; Dredge,
“Elect. Illum.,” Vol. I. pp. 46, 91, 95; “New Eng. Mag.” for
March 1891; Silliman’s _Journal_, Vol. XII. p. 69; “Sc. Am.
Suppl.,” Nos. 198, p. 3148; 206, p. 3284; 526, p. 8404; 547, p.
8733; 652, p. 10416; _La Lum. Electrique_ for October 31, 1891,
pp. 202–203; Marcel Joubert, “Leçons,” 1882, Vol. I. pp. 495,
559; 576; Th. du Moncel, “Exposé des App. de l’Elec.,” 1872,
Vols. I and II; G. B. Prescott, “Electricity,” 1885, Vol. I. pp.
105–112; “Reports of the Smithsonian Institution” for 1857, pp.
372–380; for 1862, p. 204; for 1889, p. 444; Richard Mansill,
“New Syst. of Univ. Nat. Science,” 1887, pp. 180–185; “Faraday’s
Researches on Electrostatical Induction,” also “Faraday’s Law
of Attractions and Repulsions,” at pp. 26–30, and 647–664 of
“Reprint of Papers on Electro-statics and Magnetism,” by Sir Wm.
Thomson, London, 1884; “Essays in Historical Chemistry,” T. E.
Thorpe, London, 1894, p. 142; “Life and Letters of Thomas Henry
Huxley,” by Leonard Huxley, New York, 1901, as per Index at pp.
513–514; “Fragments of Science,” by John Tyndall, New York,
1901, Vol. I. pp. 420–443; “Jnl. of Psychological Medicine,” by
Dr. William A. Hammond, New York, 1870, pp. 555–569; “Cat. Sc.
Papers ... Roy. Soc.,” Vol. II. pp. 555–561; Vol. VI. p. 653;
Vol. VII. p. 638; “Bibl. Britan.,” Vol. XVIII, N.S. for 1821,
p. 269; “Phil. Mag. and Jour. of Science,” 1833, Vol. III. pp.
18, 37, 38, 161, 253, 353, 460, 469, and Vol. XI, 1838, pp. 206,
358, 426, 430, 538.